Conventionally, in vehicle running control, lane maintenance control for controlling a vehicle so as to ensure the running of the vehicle in a lane indicated with a white line or the like is known. An example of such a control is disclosed in Japanese Patent Laid-Open Publication No.2000-168599.
In the lane maintenance control, a white line drawn on a running road surface is recognized by a vehicle-mounted camera or the like. A steering angle is automatically controlled so that the vehicle can run along a road path indicated with the white line. As a result, the vehicle can run along a correct path without drifting from the white line drawn on the running road surface.
However, although the running without drifting from the white line is made possible by each of the above described controls, a driver has to correct steering in accordance with the behavior of the vehicle because the steering angle is merely adjusted in relation with the white line. It is desired to find a fundamental reason for imposing such a driving burden on the driver so as to ease the driving burden.
The inventors of the present invention have keenly examined the reason. As a result, they concluded that a fluctuation in the behavior of the vehicle body due to the road surface or the other external factors (road surface disturbance) caused the disturbance of the attitude of the vehicle body or the running path, and the resulting vehicle body attitude or vibration induced a disturbance component even in a steering operation itself of the driver, thereby generating the driving burden as described above.
Specifically, the running path of the vehicle is considered as an integral of ever-changing attitudes and positions of the vehicle for finite time. Therefore, when the vehicle drifts from a driving line intended by the driver due to undesired behavior of the vehicle, the driver is forced to perform a corrective operation.
It is believed that the problem of the above-described effects of driver operation disturbance or road surface disturbance is generated not only during the lane maintenance control but also in a normal turning operation and the like and therefore is desired to be solved in the same way as described above.